Abstract
The paper records the results of a research into the comparative elastic and fatigue torsion strengths of bars of circular, square, and rectangular cross-sections.
The static torsion tests reveal that in the case of square and rectangular sections the use of enlarged ends leads to discrepancies between the experimental and theoretical values of the elastic torsion strengths.
The fatigue torsion tests disclose astonishing fatigue weaknesses in square and rectangular bars, the weaknesses being masked when the ends of the specimens are enlarged.
The fatigue torsion strengths of square and rectangular bars are compared with the fatigue torsion strengths of circular shafts with keyways and it is emphasized that outstanding fatigue weakness may be associated with certain forms of stress distributions even when high stress concentrations are absent.
Consideration is given to the value of the static properties of metals as safe criteria of fatigue strengths.
In an appendix the problem of the raising of the elastic stress in a material when the distribution of stress is uneven is discussed.
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